New: Choose default kernel configuration depending on the current architecture selected.
https://bugs.busybox.net/show_bug.cgi?id=5480
Summary: Choose default kernel configuration depending on the
current architecture selected.
Product: buildroot
Version: unspecified
Platform: Other
OS/Version: Linux
Status: NEW
Severity: enhancement
Priority: P5
Component: Other
AssignedTo: unassigned at buildroot.uclibc.org
ReportedBy: rsanchezs at infoglobal.es
CC: buildroot at uclibc.org
Estimated Hours: 0.0
Created attachment 4526
--> https://bugs.busybox.net/attachment.cgi?id=4526
linux: Choose default kernel configuration depending on the current architecture selected.
Hello:
I've found out that after initial configuration, including enabling of linux
kernel compilation, the default kernel config is not set and almost all make targets fail with:
"linux/linux.mk:304: *** No kernel defconfig name specified, check your BR2_LINUX_KERNEL_DEFCONFIG setting."
One possible solution would have been tweaking the build system to avoid that
message or at least, be able to run the linux-menuconfig target. I didn't find an easy way to do this and therefore I chose another option which is setting kernel default configs depending on target architecture.
Find the patch attached, regards,
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Quoted 7 lines · bugzilla at busybox.net
I've found out that after initial configuration, including enabling of linux
kernel compilation, the default kernel config is not set and almost all make targets fail with:"
linux/linux.mk:304: *** No kernel defconfig name specified, check yourBR2_LINUX_KERNEL_DEFCONFIGsetting."
Quoted 7 lines
One possible solution would have been tweaking the build system to avoid that
message or at least, be able to run the linux-menuconfig target. I didn't find an easy way to do this and therefore I chose another option which is setting kernel default configs depending on target architecture.Find the patch attached, regards,
Maybe a better option is to default to using the arch-dependent 'defconfig'
target in the kernel itself. It doesn't exist for microblaze but it's more maintainable for the other archs at least.
Especially our x86 users will be happy with this change, I think.
Patch follows.
Regards,
Arnout
Signature · 6 lines
Arnout Vandecappelle arnout at mind be Senior Embedded Software Architect +32-16-286540 Essensium/Mind http://www.mind.be G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle GPG fingerprint: 7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F
PATCH 1/1 linux: add default defconfig
Buildroot currently requires a defconfig to be supplied for the kernel:
either a custom supplied one, or one from the kernel tree. However, the kernel can (usually) also select a default defconfig, based on the architecture. So make this option available to buildroot.
We also make this the default, so the user can compile a kernel with minimal effort.
Microblaze currently (linux-3.5) doesn't have a default defconfig. Older versions also lack it for some architectures (e.g. mips was introduced in 2.6.35) but that's nearly impossible to check for at buildroot level.
--- linux/Config.in | 8 +++++++- linux/linux.mk | 15 ++++++++++++++- 2 files changed, 21 insertions(+), 2 deletions(-)
linux/Config.in +7 -1
@@ -101,7 +101,13 @@ config BR2_LINUX_KERNEL_PATCH choice prompt "Kernel configuration" - default BR2_LINUX_KERNEL_USE_DEFCONFIG + # microblaze doesn't have an in-kernel defconfig (as of 3.5) + default BR2_LINUX_KERNEL_USE_DEFCONFIG if BR2_microblazeel || BR2_microblazebe + default BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG + +config BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG + bool "Using the default supplied by the kernel" + depends on !(BR2_microblazeel || BR2_microblazebe) config BR2_LINUX_KERNEL_USE_DEFCONFIG bool "Using a defconfig"
linux/linux.mk +14 -1
@@ -146,6 +146,13 @@ endef LINUX_POST_PATCH_HOOKS += LINUX_APPLY_PATCHES +ifeq ($(BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG),y) + +define LINUX_BASE_CONFIGURE_CMDS + $(TARGET_MAKE_ENV) $(MAKE1) $(LINUX_MAKE_FLAGS) -C $(@D) defconfig +endef + +else # BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG ifeq ($(BR2_LINUX_KERNEL_USE_DEFCONFIG),y) KERNEL_SOURCE_CONFIG = $(KERNEL_ARCH_PATH)/configs/$(call qstrip,$(BR2_LINUX_KERNEL_DEFCONFIG))_defconfig
@@ -153,10 +160,16 @@ else ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG),y) KERNEL_SOURCE_CONFIG = $(BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE) endif -define LINUX_CONFIGURE_CMDS +define LINUX_BASE_CONFIGURE_CMDS cp $(KERNEL_SOURCE_CONFIG) $(KERNEL_ARCH_PATH)/configs/buildroot_defconfig $(TARGET_MAKE_ENV) $(MAKE1) $(LINUX_MAKE_FLAGS) -C $(@D) buildroot_defconfig rm $(KERNEL_ARCH_PATH)/configs/buildroot_defconfig +endef + +endif # BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG + +define LINUX_CONFIGURE_CMDS + $(LINUX_BASE_CONFIGURE_CMDS) $(if $(BR2_ARM_EABI), $(call KCONFIG_ENABLE_OPT,CONFIG_AEABI,$(@D)/.config), $(call KCONFIG_DISABLE_OPT,CONFIG_AEABI,$(@D)/.config))
Signature · 1 line
tg: (666eb02..) t/kernel-defconfig (depends on: master)
PATCH 1/1 linux: add default defconfig
Arnout, All,
Quoted 8 lines · On Sunday 02 September 2012 17:05:41 Arnout Vandecappelle (Essensium/Mind)…
Buildroot currently requires a defconfig to be supplied for the kernel:
either a custom supplied one, or one from the kernel tree. However, the kernel can (usually) also select a default defconfig, based on the architecture. So make this option available to buildroot.We also make this the default, so the user can compile a kernel with minimal effort.
Quoted 6 lines
Microblaze currently (linux-3.5) doesn't have a default defconfig. Older versions also lack it for some architectures (e.g. mips was introduced in 2.6.35) but that's nearly impossible to check for at buildroot level.
Regards,
Yann E. MORIN.
Signature · 6 lines
.-----------------.--------------------.------------------.--------------------. | Yann E. MORIN | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: | | +33 662 376 056 | Software Designer | \ / CAMPAIGN | ___ | | +33 223 225 172 `------------.-------: X AGAINST | \e/ There is no | | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL | v conspiracy. | '------------------------------^-------^------------------^--------------------'
PATCH 1/1 linux: add default defconfig
In reply to Arnout Vandecappelle (Essensium/Mind)Dear Arnout Vandecappelle (Essensium/Mind),
Quoted 8 lines · Arnout Vandecappelle (Essensium/Mind)
Buildroot currently requires a defconfig to be supplied for the kernel:
either a custom supplied one, or one from the kernel tree. However, the kernel can (usually) also select a default defconfig, based on the architecture. So make this option available to buildroot.We also make this the default, so the user can compile a kernel with minimal effort.
Quoted 6 lines
Microblaze currently (linux-3.5) doesn't have a default defconfig. Older versions also lack it for some architectures (e.g. mips was introduced in 2.6.35) but that's nearly impossible to check for at buildroot level.
I'm not sure I agree with this one. On many architectures, the default defconfig doesn't necessarily make sense. For example, on ARM, the default defconfig is versatile, which is very unlikely to match the user's hardware.
In the current situation, if the user only enables the "Linux kernel", he gets an error at build time telling him that building a kernel without specifying a configuration is not possible. I think this is a sane behavior that should be preserved.
With this patch, the user will enable "Linux kernel", not notice that it should be configured, do the build, and then try to boot the kernel on some hardware platform... and get something that doesn't work at all.
So I believe here that "compiling a kernel with minimal effort" is not possible. You _have_ to select a configuration.
The only architecture on which I believe this would make sense are i386 and x86_64, because the kernel only provides one defconfig for each of them. In this case, something like:
config BR2_LINUX_KERNEL_DEFCONFIG
string "Defconfig name"
depends on BR2_LINUX_KERNEL_USE_DEFCONFIG
+ default "i386" if BR2_i386
+ default "x86_64" if BR2_x86_64
would be sufficient. Even though some defconfig contain so many options enabled that they take ages to build, and are a bit irrelevant to build a kernel for an embedded system, but that's a different story.
Best regards,
Thomas
Signature · 4 lines
Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com
[Buildroot] [Bug 5480] Choose default kernel configuration depending on the current architecture selected.
In reply to bugzilla at busybox.nethttps://bugs.busybox.net/show_bug.cgi?id=5480
Thomas Petazzoni <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |WONTFIX--- Comment #1 from Thomas Petazzoni <[email protected]> 2013-05-26 09:29:44 UTC --- I believe that the current behavior is the one that we want. The kernel
configuration is something that's highly specific to the target hardware, so we
can't just chose some arbitrary kernel configuration for each particular architecture. I very much prefer the current behavior in which the user is
warned that he should set a kernel configuration, rather than the behavior
proposed by the patch, where Buildroot would automatically select some random configuration, the user will not notice, try to boot the kernel on whatever
hardware, and see it not boot at all.
Also, if we would be doing that for the kernel, we would have to do that for U-Boot and Barebox. And for bootloaders, the fact that we can't decide a good "default" configuration for each particular architecture is well known.
The only thing we /might/ do is define the default kernel configuration to be i386 for i386 and x86_64 for x86-64, since those two architectures have only one single kernel defconfigs. But for the other architectures, I don't think it makes sense.
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